/**
 * 从键盘输入一个数, 判断这个数是不是素数
 */
#include <stdio.h>

int main() {
	int a, b, c = 0;
	scanf("%d", &a);

	b = a;
	do {
		b --;
		if (a % b == 0) {
			c = c + 1;
		}
	} while (b > 0);

	if ( c > 1) {
		printf("%d is not a prime number \n", a);
	} else {
		printf("%d is a prime number \n", a);
	}

	return 0;
}

// 有问题,运行报错: Floating point exception (core dumped)